which water pump to buy?

[rick3000]

Lots of threads on this.

Buy a Pierburg (OEM supplier), same as the one in the Porsche box for a lot less. Metal impellers are fine if you don't mind the risk of boring a hole into your engine casing.

[BoxsterSteve]

Rick nailed it.
All the shop owners & mechanics on here subscribe to this as well, with the view that the pump is a put on a replacement schedule to mitigate chances of bearing and impeller failure.